Charleston, West Virginia (CNN) -- He was raised an orphan of the West Virginia coal mines years before the Great Depression.

On Friday -- as his body made a final return to the state he loved -- Sen. Robert C. Byrd was remembered as a political titan, champion of the poor, and defender of the Constitution.

Political leaders from both parties and every corner of the country came together at the start of the Independence Day weekend to pay homage to America's longest serving member of Congress, who died Monday at the age of 92.

President Barack Obama, former President Bill Clinton, Vice President Joe Biden, House Speaker Nancy Pelosi, Senate Majority Leader Harry Reid and Senate Minority Leader Mitch McConnell were among the mourners who gathered at a memorial service in Charleston for the veteran legislator.

Byrd was "somebody who knew how to keep the faith with his state, with his family, with his country and his Constitution," Obama said, standing before a packed, sun-splashed state capitol. "His life bent towards justice ... (and) immeasurably improved the lives of West Virginians."

Video: Pres. Obama: Byrd a 'Senate icon'

Video: Sen. Robert Byrd remembered

He "possessed that quintessential American quality," Obama said. "And that is a capacity to change, a capacity to learn ... and a capacity to be made more perfect."

Victoria Kennedy, the widow of Massachusetts Sen. Ted Kennedy, said her husband considered him "a modern incarnation of ancient virtues. A Roman of West Virginia."

"Someone will take Robert Byrd's seat," she said. "But no one will ever take his place."

Byrd, who first entered Congress at the end of the Truman administration, was known as a master of the Senate's arcane rules and a staunch defender of congressional power.

His speeches often were laced with poetry and references to the Greek and Roman classics. He typically punctuated his remarks by the brandishing of a well-worn pocket copy of the Constitution.

Over the course of his long public career, Byrd came to be "seen as the very embodiment of the Senate," Obama said. But "his passion for the Senate's past ... was not an obsession with the trivial or the obscure." It was born of a recognition of the fact that "we are not a nation of men. We are a nation of laws."

Byrd also was known as the "King of Pork," using powerful positions in Congress to steer federal spending to his home state -- one of the nation's poorest. Much of that funding famously went toward infrastructure improvements, most notably road and bridge construction.

Clinton recalled an occasion when, soon after he became president, he told Byrd that "if you pave every single inch of West Virginia, it's going to be much harder to mine coal." Byrd, in response, said that "the Constitution does not prohibit humble servants from delivering whatever they can to their constituents."

Byrd's remains lay in repose in the Senate chamber on Thursday -- a rare honor accorded to only two other senators since World War II. His casket was displayed on the same catafalque used for Abraham Lincoln, John F. Kennedy, Ronald Reagan and Thurgood Marshall, among others.

"The Senate was Robert C. Byrd's cathedral (and) West Virginia was his heaven," Biden said Friday. "There's not a lot of hyperbole in that."

Obama has ordered flags on federal buildings to fly at half-staff through Tuesday, except on Independence Day. A proclamation issued by the president said the order was given "as a mark of respect for (Byrd's) memory and long-standing service."

Byrd will be buried Tuesday after a funeral service in Arlington, Virginia.